Method for well workover operations

ABSTRACT

Method and apparatus for providing tubing pack off for well operations and includes a pair of spaced apart stripper rubbers for packing off tubing in a tubular stripper assembly and which form an annular chamber between the tubular stripper assembly and the tubing. Ports are provided in the stripper assembly for use in flowing coolant into such chamber to prevent thermal damage to the stripper rubbers. A thermal pack off means is provided to cooperate with the above described stripper assembly to form a composite stripper assembly particularly useful during shut in periods.

United States Patent Hutchison 1 Aug. 5, 1975 [5 METHOD FOR WELL WORKOVER 3,126,960 3/1964 Woodward et a1. 166/256 3,142,336 7/1964 DOSChGl 166/57 3,456,734 7/1969 Dean et a1. 1. 166/302 [75] Inventor: Stanley 0. Hutchison. k r fi l 3,498,381 3/1970 Earlougher, Jr. 166/303 Calif.

[73] Assigneei Chevron Research Company, San Primary E.\'aminerS tephen J, Novosad Francisco, Calif Attorney, Agent, or Fzrm-R. L. Freeland, Jr.; E. J.

Keeling [22] Filed: Apr. 29, 1974 [2]] Appl. No.: 465,003

Related U.S. Application Data Division of Ser. No. 274,684, July 24, 1972, Pat. No. 3,840,072,

US. Cl. 166/250; 166/302; 166/315 Int. Cl E2lb 33/124; E21b 47/10 Field of Search 166/302, 250, 303, 314,

[56] References Cited UNITED STATES PATENTS 2,642,942 6/1953 Reynolds 166/57 [57] ABSTRACT 1 Claim, 4 Drawing Figures PATENTED AUB 51975 SHEET FIGS METHOD FOR WELL WORKOVER OPERATIONS This is a division of application Ser. No. 274,684, filed July 24, 1972, now US. Pat. No. 3,840,072.

FIELD OF INVENTION This invention relates to well operations and, more particularly, this invention relates to a method and apparatus useful in performing work on completed wells. The method and apparatus of the invention is particularly useful in providing tubing pack off when operations such as steaming or foam cleanout are done on a well.

BACKGROUND OF THE INVENTION After a well has been drilled into an oil producing formation it is completed to prepare it for oil production. Usually a production liner is placed in the well and located adjacent the oil producing formation. The liner has slots or holes to permit oil to move from the formation into the well. A string of casing is connected to the liner and extends up the well to the surface. A wellhead is connected to the casing at the surface. Various production tubing and pumps or other lift devices go into the well through the wellhead to provide for flowing oil from the producing formation to the surface.

During the production life of such a well it is often desirable to perform stimulation or workover operations on the well. One such stimulation operation often performed on wells is steam injection. A type of steam stimulation often used is known as huff and puff. In such an operation steam is injected through a well into a formation, the well is then shut in for a time to soak and then later oil is produced through the same well.

It is necessary to keep close control on the well during steam injection, soaking and returning the well to production. Various stripper and auxiliary wellhead apparatus have heretofore been used to facilitate steaming of a well and returning it to production. A serious problem has been encountered however in returning a well back to production after steam stimulation due to the tendency of the well to become extremely hot sometimes to such an extent that failure of rubber strippers in the wellhead occurs. In prior art practice because of wellhead equipment limitations it was often necessary to kill the well by dumping oil or water down the well when putting the well back on production after steam injection. This was often necessary because it was not possible to determine safely if certain rubber strippers had failed. There is thus need for new stripper assemblies which are useable on a wellhead during workover operations which have backup and safety features which will facilitate controlling and producing wells.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a tubing stripper assembly for use in well operationsv An elongated tubular section which may be made up of numerous collars and adapter subs is adapted to be connected to the upper portion of a well casing. Generally the tubular section is connected above an existing wellhead. The tubular section is adapted to interiorly receive a tubular stinger having a smaller diameter than the interior diameter of the tubular section. A lower rubber stripper means is connected to the tubular section to pack off the annular space between the interior of the tubular section and the tubular stinger inserted into the tubular section. The upper and lower stripper means cooperate to form a first annular chamber in the tubular section. First port means are formed in the tubular section between the lower stripper rubber means and the upper stripper rubber means to provide entry into the first annular chamber. The first port means are provided with a flow conduit having valve means for controlling flow from the first annular chamber located interiorly of the tubular section through the first port means.

Thus in accordance with the invention during well operations in which excessive heat may be a problem the lower stripper means in particular may be cooled to prevent heat damage by introducing cooling water through the first port means into the first annular chamber. Such introduction of cooling water may be done during conduct of well operations or during inactive periods While steam soaking for example is taking place. Additionally, the first port means is useful to monitor outflow from the first annular chamber to indicate if the lower stripper means has failed and, therefore, if additional precautions must be taken during operation of the well.

If desired an auxiliary first port means may be formed in the tubular section adjacent the first annular chamber. The auxiliary first port means is provided with a flow conduit and a valve for controlling flow therethrough. When the tubular section is so arranged cooling water may be circulated through the first annular chamber to cool the stripper means. Thus water is injected through one of the first ports and Withdrawn through the other.

In accordance with a further embodiment of the invention which is particularly useful in combination with the lower and upper stripper means when the well is shut in a thermal packing means is used to pack off the tubular section and the tubular stinger above the upper stripper means. The use of the thermal packing means is particularly appropriate when a steam injection operation is closed down for the night and it is desired to leave the wellhead assembly in place. One or more thermal ports may be provided in the tubular section to give access to the annular space between the thermal packing means and the upper stripper means. Suitable valves and conduits are connected to the thermal ports and are utilized for cooling water circulation or for checking the stripper means.

PRINCIPAL OBJECT OF THE INVENTION The principal object of the present invention is to provide a method and apparatus useful at the wellhead of high temperature wells to improve control and safety during various operations at such wells. Further objects and advantages of the present invention will become apparent from the following description and the drawings which are made a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view with portions broken away for clarity of presentation and illustrates the preferred form of apparatus of the invention connected in operational fashion on a well;

FIG. 2 is a sectional view and illustrates in more detail the preferred embodiment of apparatus assembled in accordance with the present invention;

FIG. 3 is an elevation view with portions broken away for clarity of presentation and illustrates an additional embodiment of apparatus of the invention connected for temporary shut in periods in a well; and

FIG. 4 is a sectional view and illustrates in more detail the embodiment of apparatus shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of apparatus assembled in accordance with the present invention for operational use in a well is shown in FIGS. 1 and 2. For example, the present apparatus as so assembled would be useful in a steam injection project or a related foam cleanout or other well workover operation where it is desired to maintain close control on the well. FIG. 1 is an elevation view with portions broken away for clarity of presentation illustrating the apparatus of the present invention connected to a well and shows additional well equipment and underground formations. FIG. 2 is a sectional view showing the preferred embodiment of apparatus of the invention in greater detail.

The apparatus of the present invention is indicated generally by the number 43 in both FIGS. 1 and 2. It is particularly useful in providing tubing pack off when an operation such as steaming or foam cleanout is done on the well. Thus the dual tubing stripper assembly 43 is shown connected by a suitable collar 19 and coupling 17 to a wellhead base plate 15. The base plate is in turn connected to well casing 16 by means ofa suitable sub 13. The well casing extends down the well into the earth formation 12 and is usually cemented in place. A blooie line 34 having a suitable valve 36 and a kill line 38 having a valve 40 are connected at suitable ports in the collar 19 to provide access to the annulus between the tubing 14 and casing 16 for removal or injection of fluids into or out of the annulus.

The dual tubing stripper assembly 43 is connected to the upper end of upright collar 19. As described in more detail below, the assembly 43 has a pair of vertically spaced apart stripper means for packing off the annulus between the tubing and the interior wall of the tubing assembly. One of the stripper rubbers is located below outlet tubes 50 and 56 and the other stripper rubber is located above outlet tubes 50 and 56. Suitable valves 48 and 55 control flow in tubes 50 and 56, respectively.

A top assembly 68 for the tubing stripper assembly 43 is connected above outlet tubes 50 and 56. Lugs 70 and 72 are useful in threadably connecting and disconnecting the top assembly 68. A tubing stinger 32 is slideably received inside of the top assembly and the dual tubing stripper assembly 43. The stinger 32 is threadably connected to the tubing string 14. A power swivel 30 is connected to the top of the tubing stinger 32 and thus to the tubing 14. The tubing string 14 is reciprocated when desired by means of elevators 28 which are connected to the power swivel 30.. Fluid is injected into or withdrawn from the tubing string through lines 18 and 20 which are connected by flexible line 26 to the power swivel. Valves 24 and 22 are provided to control flow through lines 18 and 20, respectively.

In FIG. 2 the tubing stripper assembly indicated generally by the number 43 is shown in greater detail. The stripper assembly is connected to the upright collar 19 extending from the wellhead by means ofa stripper collar 52. A lower stripper rubber means 54 is also connected within collar 52 and is adapted to contact the tubing stinger 32 or tubing 14 which is inserted through the stripper assembly. The stripper rubber desirably prevents flow of fluids within the annulus between the tubing 32 and the inside of the collars 19, 52.

A ring spacer 67 is connected above stripper collar 52 by suitable means such as welding. The ring spacer 67 is provided with a first port in the form of a tapped hole 51 for an outlet to 50 to allow communication with the annular space 31 formed between the inside of the tubing assembly and the tubing stinger. The ring spacer 67 may also be provided with an auxiliary first port in the form of a tap hole such as indicated by the number 53. An auxiliary conduit 56 is inserted into the hole to also provide for communication with the annu lar space.

An upper stripper rubber means 62 is contained at the upper end of collar 58. The upper stripper rubber 62 also engages against tubular stinger 32 to desirably prevent flow in an upward direction in the annular space 31 between the inside of the tubing stripper assembly and the tubing stinger.

A top assembly 68 is turned down on collar 58 and retains upper stripper rubber means 62 in place to prevent flow out of the top of the assembly. Thus threaded collar 69 engages the threads in collar 58 and as the top assembly 68 is rotated downwardly the packing is made The present invention provides a tubing stripper assembly 43 for use in a well operations. An elongated tubular stripper assembly 43 which may be made up of numerous collars and adapter subs is adapted to be connected to the upper portion of a well casing. Generally the tubular stripper assembly is connected above an existing wellhead. The tubular assembly 43 is adapted to interiorly receive a tubular stinger 32 having a smaller diameter than the interior diameter of the tubular stripper assembly. A lower rubber stripper means 54 is connected to the interior of the tubular stripper assembly to pack off the annular space 31 between the stripper assembly and a tubular stinger 32 inserted into the stripper assembly 43. An upper rubber stripper means 62 spaced apart from the lower stripper means 54 is connected to the tubular stripper assembly to pack off the annular space 31 between the interior of the stripper assembly and the tubular stinger 32 inserted into the tubular stripper assembly. The upper and lower stripper means cooperate to form a first annular chamber 31 in the tubular stripper assembly. First port means 51 are formed in the tubular stripper assembly between the lower stripper rubber means 54 and the upper stripper rubber means 62 to provide entry into the first annular chamber 31. The first port means 51 are provided with a flow conduit 50 having valve means 48 for controlling flow from the first annular chamber 31 located interiorly of the tubular section through the first port means 51.

Thus, in accordance with the invention, during well operations in which excessive heat may be a problem, the lower stripper means 54 in particular may be cooled to prevent heat damage by introducing cooling water through the first port means 51 into the first annular chamber 31. Such introduction of cooling water may be done during the actual conduct of well operations or during inactive periods, for example, while steam soaking is taking place. Additionally, the first port means 51 is useful to monitor outflow from the first annular chamber 31 to indicate if the lower stripper means 54 has failed and, therefore, if additional precautions must be taken during operation of the well. Escaping steam from the first port means 51, for example, would indicate that the stripper rubber had failed and that the well should be operated accordingly.

If desired, an auxiliary first port means 53 may be formed in the tubular stripper assembly adjacent the first annular chamber 31. The auxiliary first port means 53 is provided with a flow conduit 56 and a valve 55 for controlling flow therethrough. When the tubular stripper assembly is so arranged cooling water may be circulated through the first annular chamber 31 to cool the stripper means. Thus water is injected through one of the first ports 51 and withdrawn through the other 53 to cool the stripper rubber. The rate of flow of the water should be such as to insure that failure of the stripper rubber does not occurv DESCRIPTION OF THE ADDITIONAL EMBODIMENT In accordance with the invention additional components are added to the tubing stripper assembly to permit added flexibility and additional safety when the apparatus of the present invention is used. Such an additional embodiment is described in detail in FIGS. 3 and 4. Where components in such FIGS. 3 and 4 are identical with components illustrated in FIGS. 1 and 2, identical numbers are used to facilitate an understanding of the invention.

The additional embodiment of the invention is particularly useful in combination with the lower and upper stripper means of the preferred embodiment when the well is shut in. In such further embodiment a thermal packing means is used to pack off the annular space be tween the tubular stripper assembly and the tubular stinger above the upper stripper means. The use of the thermal packing means is particularly appropriate when a steam injection operation is closed down for the night and it is desired to leave the wellhead assembly in place. One or more thermal ports may be provided in the tubular section to give access to the annular chamber between the thermal packing means and the upper stripper means. Suitable valves and conduits are connected to the thermal ports and are utilized for cooling water circulation or for checking the stripper means.

The additional embodiment of apparatus in accordance with the present invention is shown in FIGS. 3 and 4. FIG. 3 is an elevation view with portions broken away for clarity of presentation illustrating the apparatus of the present invention connected to a well. FIG. 4 is a sectional view showing this embodiment in greater detail.

The apparatus of the additional embodiment of the present invention is indicated generally by the number 42 in both FIGS. 3 and 4. It is particularly useful in providing tubing pack off during periods when the well is shut in for a time after operations such as steaming or foaming are done on the well utilizing the preferred embodiment of apparatus of the present invention. Thus the composite tubing stripper assembly 42 is shown connected by a suitable collar 19 and coupling 17 to a wellhead base plate 15. The base plate is in turn connected to well casing 16 by means of a suitable sub 13. The well casing extends down the well into the earth formation 12 and is usually cemented in place. A blooie line 34 having a suitable valve 36 and a kill line 38 having a valve 40 are connected at suitable ports in the collar 19 to provide access to the annulus between the tubing 14 and casing 16 for removal or injection of fluids into or out of the annulus.

The composite dual stripper assembly 42 is connected to the upper end of upright collar 19. As described in more detail below, the assembly 42 has a pair of vertically spaced apart stripper rubbers for packing off the annulus between the tubing and the interior wall of the assembly. One of the stripper rubbers is located below outlet tubes 50 and 56 and the other stripper rubber is located above outlet tubes 50 and 56 and below outlet tube 46. Suitable valves 48, 55 and 44 control flow in tubes 50, 56 and 46, respectively.

A top assembly 68 for the stripper assembly is connected above outlet tube 46. Lugs and 72 are useful in threadably connecting and disconnecting the top assembly 68. A thermal pack off asembly, partially shown and identified by the number 74, is connected interiorly of the top assembly 68.

A tubing stinger 32 is slideably received inside of the top assembly and the composite stripper assembly 42. The stinger 32 is threadably connected to the tubing string 14. A power swivel 30 is connected to the top of the tubing stinger 32 and thus the tubing 14.

The tubing string 14 may be reciprocated by means of elevators 28 which are connected to the power swivel 30. Fluid may be injected into or withdrawn from the tubing string through lines 18 and 20 which are connected by flexible line 26 to the power swivel. Valves 24 and 22 are provided to control flow through lines 18 and 20, respectively.

In FIG. 4 the composite stripper assembly indicated generaly by the number 42 is shown in greater detail. The composite stripper assembly is connected to the upright collar 19 extending from the wellhead by means of a stripper collar 52. A lower stripper rubber 54 is also connected within collar 52 and is adapted to contact the stringer 32 or tubing which is inserted through the stripper assembly. The stripper rubber desirably prevents flow of fluids with the annulus between the tubing 32 and the inside of the collars 19, 52.

A ring spacer 67 is connected above the stripper collar 52 by suitable means such as welding. The ring spacer 67 is provided with a first port in the form of a tapped hole 51 for an outlet to 50 to allow communication with annular chamber 31. The ring spacer 67 may also be provided with additional auxiliary ports in the form of a tap hole such as indicated by the number 53. A conduit 56 is inserted into the hole to provide communication with the interior of the assembly.

An upper stripper rubber 62 is contained at the upper end of collar 58. The stripper rubber 62 also engages against tubular stinger 32 to desirably prevent flow in an upward direction in the annular chamber 31. A second ring spacer member 71 is connected to collar 58 by means of collar 60. The second ring spacer 71 contains a thermal port in the form of a tapped hole 45 which threadably engages outlet tube 46 to allow communication from outside the well to the annular space between the assembly and the tubing stinger. Additional auxiliary holes 47 may be provided in the ring spacer 71 and closed off by a suitable plug 64 until needed.

An upright adapter sub 66 is connected by suitable means such as welding to the upper portion of ring member 71. The adapter sub contains a thermal pack off assembly for packing off the tubing to prevent flow at the upper end of the assembly. The tubing pack off assembly includes a sleeve 74 threadably engaged into a collar 65. Collar 65 contains an insert sleeve 76 and thermal packing members 78 and 80. When the top assembly 68 is turned down the packing assembly engages against the stinger tubing 32 to prevent flow out of the top of the assembly. Thus threaded collar 69 engages the threads in adapter sub 66 and as the top assembly 68 is rotated downwardly the packing is made up. Thus the composite tubing assembly is provided with a thermal pack off seal at its top which may be easily added or removed from the preferred embodiment to give greater safety and versatility in well operations.

SUMMARY OF ADVANTAGES OF THE INVENTION curred. A thermal packing means may, when desired, be added to the tubing stripper assembly above the rubber strippers to give added pack off protection.

Although certain embodiments of the invention have been described in detail, the invention is not to be limited to only such embodiments but rather the invention is meant to include all aspects of the method and apparatus encompassed by the appended claims.

I claim:

1. A method of well workover comprising connecting a tubular sectin to the upper portion of a well casing, inserting a tubing stinger into the well through said tubular section, said tubular section having a larger interior diameter than the exterior diameter of said tubing stinger, packing off the annular space in spaced apart locations between said tubular section and said tubing stinger with an upper pack off means and a lower pack off means to form an annular chamber, forming a first port in said tubular section to establish communication with said annular chamber, forming an auxiliary port in said tubular member to establish communication with said annular chamber, flowing a fluid through said first port into said annular chamber to cool said pack off means, flowing fluid out of said annular chamber through said auxiliary port and monitoring the outflow from said auxiliary port to determine if the lower pack off means has failed. 

1. A method of well workover comprising connecting a tubular sectin to the upper portion of a well casing, inserting a tubing stinger into the well through said tubular section, said tubular section having a larger interior diameter than the exterior diameter of said tubing stinger, packing off the annular space in spaced apart locations between said tubular section and said tubing stinger with an upper pack off means and a lower pack off means to form an annular chamber, forming a first port in said tubular section to establish communication with said annular chamber, forming an auxiliary port in said tubular member to establish communication with said annular chamber, flowing a fluid through said first port into said annular chamber to cool said pack off means, flowing fluid out of said annular chamber through said auxiliary port and monitoring the outflow from said auxiliary port to determine if the lower pack off means has failed. 